1. Field of the Invention
The present invention relates generally to the art of wood preservation, and more particularly to the art of increasing the resistance of pressure permeable wood species to the deterioration caused by weathering, leaching or attack by fungi, insects, marine borers, etc. In the principal embodiments of the present invention, such wood preservation is accomplished by using as an impregnating agent a vegetable extract containing tannin which has been halogenated. Still more specifically, in the preferred embodiment the halogenation is accomplished with bromine.
2. Description of the Prior Art
It has been known for many years that certain woods of various types can be preserved by chemical treatment. Creosote, pentachlorophenol, and certain mixtures of copper, chromium and arsenic referred to as "CCA" are several of the better known examples. All of such treatment systems involve one or more drawbacks, principally because they are highly toxic or because they leach from the wood material, thereby leaving the wood unprotected. Other systems are known for coloring wood and many prior art patents describing early attempts at wood preservation are disclosed in U.S. Pat. No. 4,732,817 issued Mar. 22, 1988 to W. Robert Lotz and Donald F. Hollaway for "Wood Preservation".
The aforementioned Lotz, et al. patent not only describes the problems with the prior art but suggests a solution for the problem in which a tannin extract is taken from a plant species which has relatively superior weathering and other resistance properties. Wood to be treated is impregnated with the extract, which is then further processed with an aqueous solution of a fixative to prevent leaching of the extract during use of the wood. The process described in the Lotz, et al. patent can be used not only for wood preservation, but for coloring of the wood and, in that connection, certain metallic salts could also be used. Methods for treating wood in an environmentally suitable manner would represent substantial advances in the art. Products prepared therefrom could be used for aesthetic enhancement or for structural purposes. One feature which has been of some concern with regard to the Lotz, et al. system is the requirement of the use of a fixative, the elimination of which, at least for some applications, would represent a further advance in this technology.